1. Field of the Invention
The present invention relates to an analog-digital hybrid integrated circuit provided with an initial set-up circuit.
2. Description of the Prior Art
An integrated circuit is provided with an initial set-up circuit for internal logical circuits.
For example, such an initial set-up circuit for use in a integrated circuit is as illustrated in FIG. 1. In FIG. 1, an integrated circuit LSI1 is reset when the voltage on its reset terminal RST becomes less than a prescribed threshold level due to a reset terminal RESET of an internal logical circuit LGC1 changing to a high (H) level via a Schmitt trigger inverter circuit IN. A capacitor C1 receives power source voltage E via a resistor R1 and provides a potential to the reset terminal RST.
A potential V1 on the reset terminal RST changes as follows when the power source E is turned on: EQU V1=E(1=.epsilon..sup.-t/C1R1) (1)
Hereupon, the inverter IN keeps the H level and hence the internal logical circuit LGC1 stays reset until the potential V1 reaches the threshold of the inverter IN. Thereafter, provided the potential exceeds the threshold value after the passage of a prescribed period of time, the inverter IN changes to a low level L to release the reset to permit ordinary operation to be started thereafter.
However, the integrated circuit, when fabricated as an analog-digital hybrid LSI circuit, must have many input and output terminals and hence is limited in its package size so as to often result in insufficient space for providing a terminal for use as the reset terminal.